This invention relates to a data distributor for use in a time division multiple access network and to a distribution device comprising a plurality of the data distributors.
In general, a plurality of data distributors are arranged in rows and columns in a housing or frame of a distribution device. The data distributors are given position signals determined by positions of the data distributors in the distribution device. The position signals are made to correspond to distributor numbers assigned to the data distributors and may be called distributor number signals representative of the distributor numbers.
The data distributors are supplied with an input data signal which is multiplexed in a time division fashion and which is divisible into a plurality of partial or channel data signals assigned to a plurality of channels, namely, time slots, respectively. A sequence of channel number signals is also given to the data distributors in synchronism with the corresponding partial data signals so as to specify the channels for the respective partial data signals.
As will later be described with reference to a few figures of the accompanying drawing, a conventional distribution device comprises a plurality of data distributors each of which compares the position signal assigned to the data distributor with the channel number signal sequence to produce an enable signal on coincidence between the assigned position signal and one of the channel number signals. The data distributor allows a part of the input data signal to pass therethrough during presence of the enable signal and distributes the part of the input data signal to an output port thereof as an output data signal.
In the conventional distribution device, let one of the data distributors distribute one of the partial data signals for a preselected one of the channels and be stalled for same reason or other. In order to avoid interruption of distribution, it may be considered that a spare data distributor is prepared in the distribution device and substitutes distribution of the one partial data signal for the one data distributor. For this purpose, the spare data distributor should be supplied with one of the position signals assigned to the one data distributor. However, the position signals are determined by the positions of the data distributors and are therefore invariable in the respective data distributors.
This means that the channel number signals must be altered so as to carry out substitution of the data distributors. Alteration of the channel number signals is practically difficult in the conventional distribution device, as will later be described. Accordingly, interruption of distribution is inevitable when the data distributor or distributors are stalled.
Thus, the position signals are made to correspond to the channels of the input data signal, respectively, and are representative of positions, namely, spaces for the respective data distributors. Taking this into consideration, it is assumed that an idle channel is included in the channels. In this case, an unused one of the spaces must be left for the idle channel in the distribution device despite the fact that no data distributor may be accommodated in the useless space. Therefore, the conventional distribution device becomes uselessly bulky in structure.